The U.S. economy grew at an annual rate of 2.4 percent in the second quarter, slower than the previous two quarters, according to the preliminary estimate released Friday by the Commerce Department.

The figures represent a further slowdown in economic growth compared with a remarkable 5.6 percent surge in the fourth quarter of 2009 and a newly-revised 3.7 percent rise in the first quarter of 2010. Economists had expected a 2.5 percent rise in the three months ended in June.

The U.S. government usually releases three estimates of the quarterly Gross Domestic Product (GDP) -- the output of goods and services produced by labor and property located in the United States.

The deceleration was primarily caused by a slowdown in consumer spending, which accounts for about 70 percent of the overall economy.

Personal consumption expenditures rose 1.6 percent in the second quarter, compared with an increase of 1.9 percent in the first.

The weaker performance was also a result of less growth in business inventory buildup, which was a main driver of growth in early stages of the recovery.

The International Monetary Fund (IMF) said Friday that the U.S. economic recovery has been slow and the outlook remains uncertain with rising downside risks, which warrants further policy stimulus to keep recovery on track.

"Looking ahead, risks are elevated and tilted to the downside, with particular risks from a double dip in the housing market and spillovers if external financial conditions worsen," the IMF said in its annual assessment of the U.S. economy and policy response.